1. Field of the Invention
The present invention relates to a capacitor used in various types of electronic appliances, and more specifically, to a chip solid electrolytic capacitor having a solid electrolyte made of conductive polymer.
2. Background Art
Electronic appliances are being designed to operate at higher and higher frequencies; consequently, capacitors as an electronic component are being required to have excellent impedance characteristics in higher frequencies than before. In order to meet this demand, various types of solid electrolytic capacitors are being developed which have a solid electrolyte made of conductive polymer high in electric conductivity.
On the other hand, solid electrolytic capacitors used in the CPU periphery of personal computers are strongly expected to shrink in size and grow in capacity. Furthermore, as circuits are operated at higher and higher frequencies, capacitors are strongly required to have not only lower ESR (Equivalent Series Resistance) but also lower ESL (Equivalent Series Inductance) as well as excellent noise rejection and excellent transient response.
FIGS. 10A to 10C show the structure of a conventional chip solid electrolytic capacitor. FIG. 10A is a cross sectional view showing a laminated body of capacitor elements of the capacitor, FIG. 10B is a perspective view showing the internal structure of the capacitor and FIG. 10C is a perspective view showing the external appearance of the capacitor. Each of capacitor elements 13 includes anode electrode 14, solid electrolyte layer 15 and cathode electrode 16. Anode electrode 14 is formed by roughening the surface of valve metal foil and then forming a dielectric oxide film thereon. Anode electrode 14 is provided with an unillustrated insulating portion in a predetermined position so as to be divided into an anode portion and a cathode portion. On the dielectric oxide film in the cathode portion are formed solid electrolyte layer 15 made of conductive polymer and cathode electrode 16 which are laminated in this order. A laminated body of a plurality of capacitor elements 13 is referred to as capacitor elements laminated body (hereinafter, laminated body) 17.
Anode terminal 18 includes anode electrode connection 18A to be connected to anode electrodes 14 of laminated body 17. Cathode terminal 19 includes cathode electrode connection 19A to be connected to cathode electrodes 16 of laminated body 17. Packaging resin 21 covers laminated body 17, anode electrode connection 18A and cathode electrode connection 19A.
In the conventional chip solid electrolytic capacitor thus structured, anode terminal 18 and cathode terminal 19 are aligned in a same plane with a distance of 0.2 to 2.0 mm between them. This arrangement allows the current for charging the chip solid electrolytic capacitor to flow in a loop, passing through anode terminal 18, anode electrode connection 18A, laminated body 17, cathode electrode connection 19A and cathode terminal 19 in this order. The loop area is so small that the ESL can be reduced to about 580 pH, for example. Such a chip solid electrolytic capacitor is disclosed in Japanese Patent Unexamined Publication No. 2004-95816.
Thus, in the conventional chip solid electrolytic capacitor, the ESL is reduced by aligning anode terminal 18 and cathode terminal 19 flush with and close to each other. However, further reduction in ESL is required in order to meet the recent demand in the market.